The Department of Energy stole a few beams of limelight from President Reagan yesterday, eliminating most of its emergency energy conservation plan and proposing a delay in the energy-efficiency labeling of household appliances.

The action came as Reagan proposed an 80 percent budget cut in energy conservation support, saying decontrol of oil prices will boost conservation automatically. He said his cuts could save $2.4 billion by 1987.

In a Federal Register notice, DOE scrapped six parts of the standby plan that former president Carter had planned to impose on states that did not meet target conservation levels during any future fuel emergency. They included alternate-day gas purchasing, compulsory four-day work weeks, stricter enforcement of the 55-mile-per-hour speed limit, lowering of temperatures in public buildings, restrictions on automobile use and employer actions to cut energy use by employes, such as subsidizing carpools or public transit.

Witnesses had told hearings in eight cities that these rules "would interfere excessively in their lives, were unnecessary restrictions and would impose costs far in excess of their benefits," the Register notice said. Two other aspects of the plan were left in effect: one is a program to provide consumer information on energy conservation, and the other would impose minimum gasoline purchase requirements to prevent "Topping-off," which has caused long gas lines in past fuel crises.

DOE also proposed to halt the issuance of efficiency standards for home appliance until there is a full review of the assumptions on which those standards have been based. The formal notice said the Department of Justice and former president Carter's regulatory analysis review group, as well as the appliance industry, had expressed reservations about the assumptions and the methods used to arrive at the standards.

Proposed and interim final standards have been issued so far for eight kinds of appliances: refrigerators, freezers, clothes dryers, water heaters, room air conditioners, kitchen ranges and ovens, central air conditioners and furnaces. Standards, for five more had been planned for the end of the year: dishwashers, humidifiers and dehumidifiers, and heat pumps. Manufacturers were to have been required to meet or exceed the energy-use limits, for an estimated total energy saving equal to 993,000 barrels of oil a day by the year 2000.

Reagan's budget proposal would ax these standards altogether. It goes further, however, also targeting building efficiency standards and public utility energy audit services.

Reagan's plan would retain the conservation tax credit but would move DOE's weatherization aid program to the Department of Housing and Urban Development and would kill programs supporting energy development from urban waste as well as grants to state and local energy offices.